The present invention addresses prior art problems relative to fitting and pipe engagement, gasket blowouts, and thrust blocking.
With fitting arrangements such as the fitting 10 shown in FIG. 1, with an associated system filled with water and pressurized, any one or various combinations of pipe weight, water weight and soil atop the pipe exerts downward force against the frontal opening of the fitting. This can create a gap between a fitting and a pipe 12 end portion therein by deformation or extrusion of the gasket about the pipe under the downward force. With high line pressure and surges, the gasket can deform, bulge outwardly and extrude out through the gap in what is termed in the art a gasket blowout, which can result in washout, erosion, etc.
In large irrigation systems, such as those utilized in golf courses, landscaping, etc., main line pipe systems generally comprise PVC pipes inserted in bell ends of gasketed ductile iron fittings. A general prior art practrice is to provide concrete thrust blocks by pouring and forming cement behind fittings that either cause a change in the direction of flow, such as the elbows, bends, tee""s, or a change in the diameter, as by reducer components. Such thrust blocks as shown at 16 in FIG. 2A and at 18 in FIG. 2B can serve to retain pipes and fittings, such as fittings 17 and 19, against disengagement. Thrust blocking, however, relies totally on stable soil conditions. In unstable soils and in imported soils, thrust blocks shift, move and thus provide no effective restraint on fittings, and result in joint separation.
There have been provided in the prior art joint restraints wherein pipes are mechanically joined to fittings. However, such arrangements result in multi-piece assemblies that require care and attention during installation and in service.
Prior art joint restraints typically comprise of two half-clamps secured together by threaded fasteners and clamped about the pipe disposed in a bell-end of a fitting. With such mechanical joint restraint systems, piping systems utilizing the same provide thrust resistance to frictional and soil bearing forces along long lengths of pipe thus joined together. In such arrangements, centering and insertion of a pipe end portion into a bell end of fitting present difficulties generally requiring two persons, one person to locate and center a pipe, and a second person to urge the pipe inwardly into a fitting. With sizable pipes, such a 6xe2x80x3 in diameter and larger, this can be an arduous task.
The present invention provides gasketed fitting arrangements wherein at the opening of the fitting, typically a bell-end style fitting, there is provided an outwardly extending integrally-formed half-clamp. Such outwardly extending protrusion provides a ledge. Upon laying a pipe end portion on the ledge, it is automatically centered and aligned for insertion. The pipe is thus readily inserted by a single person simply urging it inwardly into the bell end portion of the fitting.
With metal fittings, the half-clamp protrusion and the separate second half-clamp are preferably provided with raised serrations or ridges to be embedded into pipe end portion to prevent disengagement of the pipe from the fitting. With fittings of PVC plastic, adhesive may be applied to the clamp surfaces to prevent disengagement of the pipe from the fitting.